Technical Field
The present disclosure relates to a rare earth bonded magnet.
Background Art
A rare earth magnet has excellent magnetic properties and therefore in recent years is extensively used in rotary equipment such as motors, general home electric appliances, audio equipment, medical equipment, industrial instruments, and the like. Especially, a rare earth bonded magnet which is formed of a rare earth magnetic powder combined with a resin binder is highly flexible in terms of formation and so assists in reducing size and enhance performance in the usages described above.
The rare earth bonded magnet is further noted to have been used in vehicles (this usage is referred to as “automotive application”). A ferrite permanent magnet has been used for the common permanent magnet in automotive applications since the ferrite permanent magnets have high heat resistance and the like. Such a ferrite permanent magnet, however, exhibits a relatively low spontaneous magnetization or magnetic force, and therefore has a drawback of needing to be large in volume in order to produce a necessary magnetic flux. Consequently, in response to requests for increased output and reduced size, the rare earth magnet, which has a high spontaneous magnetization even with a small volume, is increasingly used year on year in place of the ferrite permanent magnet.
Since automobiles are exposed to various environmental conditions, permanent magnets for automotive application are required to exhibit adequate magnetic properties under a wide range of temperatures, that is to say, must not be demagnetized substantially due to temperature fluctuations while having physical heat resistance. The physical heat resistance referred to herein refers to the heat resistance relating to mechanical strengths. Generally, the rare earth permanent magnet is substantially demagnetized at high temperatures, thus presenting a heat demagnetization problem. Under such a circumstance, attempts have been made to develop rare earth magnets with magnetic properties that do not decrease a great deal at a high temperature and a method for producing the rare earth magnets (see, e.g., Japanese Patent Laid-Open No. 2015-8232).
The present disclosure was achieved under such circumstances and is intended to provide a rare earth bonded magnet with a demagnetization property with a lower demagnetization rate in response to temperature fluctuations and high physical heat resistance.